The invention relates to mechanical pupil dilators and to applicators for mechanical pupil dilators.
Light reaches the retina of the eye through the pupillary opening (the pupil) in the iris. A normal pupil is capable of reacting to light by constriction and reacting to dark by dilation in order to control the amount of light reaching the retina. In a diseased iris, such as the iris of a patient with diabetic mellitus, uveitis or chronic use of miotic eye drops, the pupillary opening remains small all of the time.
Cataract is one of the leading causes of blindness in the world. In the developed world the incidence of diabetes is increasing. Diabetic patients are well known for having small pupils. Additionally, diabetics have a higher incidence of cataract, vitreous haemorrhage and retinal detachment than the general population.
Small pupil patients pose a major problem and challenge in ophthalmic surgery. When such small pupil patients have cataract or vitreo-retinal surgery and pupil cannot be easily dilated by mydraiatic eye drops. Surgery is very difficult unless the pupil can be mechanically dilated.
It is an object of the present invention to provide a mechanical pupil dilator for use in eye surgery. It is a further object of the present invention to provide an apparatus for inserting and removing said pupil dilator.
According to a first aspect of the invention there is provided a pupil dilator comprising a discontinuous resilient ring adapted to be temporarily straightened linearly for insertion into, or removal from, the anterior chamber of the eye. The discontinuous resilient ring has first and second ends proximate each other and a periphery adapted to engage the periphery of the pupillary opening in the iris of an eye, at least the first end of the resilient ring is adapted to be engaged by a pupil dilator applicator tool.
Preferably, the resilient ring is substantially V shaped in cross-section, the vertex of the V is orientated radially inwards towards the center of the ring and the inner portion of the V provides an outwardly orientated groove adapted to engage the periphery of the pupillary opening in the iris.
The first end of the resilient ring has an aperture in it adapted for engagement by an applicator. The pupil dilator is inserted into the anterior chamber of the eye through a single corneal opening with the aid of the applicator. The ring is adapted to enlarge and stretch the pupillary opening in the iris, hence enlarging the pupil.
To aid engagement, the second end of the resilient ring is adapted to slide along the periphery of the pupillary opening by being curved radially inwards.
According to a second aspect of the invention there is provided a pupil dilator applicator including an elongate tube having first and second ends with at least the first end being open, and a retractor slidably disposed within the tube and being movable from a first position to a second position, the retractor having an grasper at one end thereof, the grasper adapted to engage a pupil dilator when the retractor is in the first position. Moving the retractor to the second position draws the pupil dilator into the tube.
The retractor is an elongate rod slidably disposed within the second end of the tube, the rod bearing the grasper at its first end within the tube and a handle at its second end external to the tube, the handle facilitates movement of the retractor between the first and second positions.
The grasper is a hook adapted to engage with the aperture in the first end of the resident ring.
The retractor is biased in the second position by a spring.
According to a third aspect of the invention there is provided a method of dilating a pupil including:
a pupil dilator comprising a discontinuous resilient ring adapted to be temporarily straightened by an applicator for insertion into, or removal from, the anterior chamber of the eye;
an applicator comprising an elongate tube having first and second ends with at least the first end open, and a retractor slidably disposed within the tube and being movable from a first position to a second position, the retractor having an grasper at one end, the grasper adapted to engage the pupil dilator when the retractor is in the first position, and wherein when the retractor is moved to the second position the pupil dilator is drawn into the tube; wherein
a first end of the discontinuous resilient ring is grasped with the grasper and the retractor moved to the second position to draw the resilient ring into the applicator tube, at the same time straightening the resilient ring,
inserting the applicator tube into the anterior chamber of an eye through an incision in the cornea or sclera,
moving the retractor from the second position to the first position so as to eject the pupil dilator from the applicator tube, and at the same time positioning the applicator tube so as to guide the ejected pupil dilator onto the periphery of the pupillary opening.
The method is performed prior to lens or vitreo-retinal surgery to enlarge the pupil.
The pupil dilator is removed in the reverse sequence by grasping one end of the resilient ring with the grasper and drawing the ring into the applicator tube, and withdrawing the applicator tube from the anterior chamber of the eye.
Further aspects of the invention will become apparent from the following description, which is given by way of example only.